With regard to a hydraulic hammering device of this type, for example, a technology disclosed in JP 61-169587 U has been known.
A hydraulic hammering device disclosed in JP 61-169587 U includes a piston that has a large-diameter section in the axially middle thereof and small-diameter sections formed in front and the rear of the large-diameter section. The piston being disposed in a slidably fitted manner into a cylinder causes a front chamber and a rear chamber to be defined individually between an outer peripheral surface of the piston and an inner peripheral surface of the cylinder.
While the front chamber is always communicated with a high pressure circuit, the rear chamber is communicated with either the high pressure circuit or a low pressure circuit alternately by a switching valve mechanism. Pressure receiving areas of a front side portion and a rear side portion are differentiated from each other so that the piston can move in the hammering direction when the rear chamber is in communication with the high pressure circuit, and this configuration enables an advance and a retraction of the piston to be repeated in the cylinder (hereinafter, also referred to as “rear chamber alternate switching method”).
While, as described above, the hydraulic hammering device disclosed in JP 61-169587 U, which employs the “rear chamber alternate switching method”, moves the piston in the hammering direction in hammering using a pressure receiving area difference, hydraulic oil on the front chamber side acts in such a way as to resist a movement of the piston in the hammering direction because the front chamber is always in communication with the high pressure circuit. Thus, to further improve hammering efficiency, there is room for improvements.
On the other hand, in for example JP 46-001590 A, a hydraulic hammering device that switches each of a front chamber and a rear chamber into communication with either a high pressure circuit or a low pressure circuit in an interchanging manner is disclosed (hereinafter, also referred to as “front/rear chamber alternate switching method”). Since, in a hydraulic hammering device employing the “front/rear chamber alternate switching method”, the front chamber is switched into communication with the low pressure circuit when a piston advances, there is no occasion that hydraulic oil on the front chamber side resists a movement of the piston in the hammering direction. Therefore, the hydraulic hammering device is suitable to improve hammering efficiency.